Preparing an ophthalmic lens for mounting in an eyeglass frame selected by a wearer comprises six main operations, of which half are generally implemented by a lens manufacturer and the other half by an optician.
The operations implemented by the lens manufacturer are the following:                molding the ophthalmic lens to a standard shape so that it presents optical power close to the desired optical power;        accurately machining one of the optical faces of the ophthalmic lens so that it presents optical power equal to the desired optical power; and        marking the ophthalmic lens so as to situate accurately particular points and the horizon axis for said lens.        
The operations performed by the optician are the following:                acquiring the outline of one of the rims or of one of the presentation lenses of the eyeglass frame selected by the client (future wearer of the eyeglass frame);        centering the lens, which consists in positioning and orienting that outline appropriately on the lens as a function of the positions of the particular points and of the orientation of the horizon line of the lens, so that once assembled the lens will be centered relative to the pupil of the wearer's corresponding eye; and then        shaping the lens, which consists in cutting it to have that outline so that it matches the shape of the selected frame both mechanically and pleasingly, while performing as well as possible the optical function for which it is designed.        
Among the various technologies that enable the centering marks on one of the optical faces of the ophthalmic lens to appear, marking by means of an ink pad that is pressed against said optical face is in widespread use because of its simplicity, its low cost, and its accuracy.
In order to protect the lens and avoid the centering marks from being rubbed off, the ophthalmic lens is generally stored in a pouch while it is being transferred from the lens manufacturer to the optician. Normally the pouch is provided with a sticker marked with an identifier and optical data about the optical powers of the lens.
On receiving the lens, the optician can input that information into a computer in order to identify the lens that has been received and verify that it does indeed correspond to the lens ordered from the manufacturer.
The main drawback of that method is that inputting such data is lengthy, time consuming, and also a source of errors.